As part of the on-going commissioning tests, we are happy to be able to report on the first spectroscopy observations made by Gaia.
You will have seen the ‘first light’ images from the early phases of commissioning already, but as part of these activities we have also started taking test spectroscopic measurements of known stars.
While astrometric measurements will determine the positions and motions of stars, Gaia will use spectroscopy to measure key physical properties, such as brightness, temperature, mass, age, and chemical composition.
This is achieved by studying stellar spectra – the fingerprints of stars. Typically, a star’s spectrum includes a broad continuum spanning a wide range of wavelengths coming from the hot gas at the surface of the star. This is then interspersed with dips at specific wavelengths, where cooler atoms and molecules in the ‘atmosphere’ of the star absorb some of the continuum light. Occasionally, brighter emission lines can also be seen. The absorption and emission lines provide an indication of the elements present in the object and under what temperature and pressure conditions they exist.
In addition, the lines can all be shifted from their normal wavelengths – that is, the corresponding wavelength at which the ...